Histological and Ultrastructural Description of Benign Adipocytic Tumors in Farmed Striped Sea Bream (Lythognathus mormyrus)

Cutaneous neoplasms affecting wild striped bream (Lythognathus mormyrus) have been recorded after their introduction in a marine aquaculture farm in the Adriatic Sea. The tumors were evident on 24% of the reared fish, showing single or multiple nodules, with a diameter ranging between 0.5–4.0 cm. Histologically, all the neoplastic lesions were located in the stratum spongiosum of the dermis and were surrounded by a thin capsule of connective tissue. The tumors were predominantly composed of adipocytes grouped and surrounded by a thin net of fibroblasts and collagen fibers. In some lipomas a mixture of adipocytes and uniform spindle cells were also observed. Fibroblasts and collagen fibers, or spindle cells, showing few mitotic figures were mainly observed in other nodules. Three of the tumors showed bands of cells with elongated nuclei. Five neoplasms differed from the classic spindle cell lipoma due to the presence of scattered giant cells. These cells presented acidophilic abundant cytoplasm with multiple hyperchromatic nuclei showing a concentric “floret-like” arrangement. The tumors were further characterized by ultrastructural observations that allowed ruling out the presence of virus-like particles within the lesions. Histological features of the masses lead to the identification of four prevalent patterns of neoplasms: lipoma, fibrolipoma, spindle cell lipoma (SCL), and atypical spindle cell-like lipoma (ASCL). The different neoplasms could arise from the transformation of mesenchymal cells of dermal origin. To the author’s knowledge, this is the first report describing key differential histological and ultrastructural features of these neoplasms in striped sea bream.

Leydig Cells in Patients with Non-Obstructive Azoospermia: Do They Really Proliferate?

Background: Non-obstructive azoospermia (NOA) is a form of male infertility caused by disorders of the testicular parenchyma and impaired spermatogenesis. This study aimed to investigate the nature of Leydig cell changes in patients with NOA, especially whether their actual proliferation occurred. Methods: 48 testicular biopsies from infertile patients with NOA and 24 testicular biopsies originating from azoospermic patients suffering from obstructive azoospermia (OA) were included in the study. Leydig cells and their possible proliferative activity were analysed by immunohistochemistry and morphometry (stereology). Results: Unlike in the OA group, Leydig cells in NOA patients were sometimes organised into larger clusters and displayed an abundant cytoplasm/hypertrophy. Moreover, significant fibrosis of the interstitial compartment was demonstrated in some NOA samples, often accompanied by inflammatory cells. Stereological analysis showed no increase/proliferation of Leydig cells; on the contrary, these cells decreased in number in the NOA group. Conclusions: The decrease in the number of Leydig cells can be explained by previous inflammatory changes within the testicular interstitium and consequent interstitial fibrosis. The interstitial fibrosis might have a deteriorating effect on Leydig cells.

PAX5 P80R mutated acute leukemia followed by genetically-related histiocytic proliferation with clonal IGH gene rearrangements

Introduction/Objective PAX5 is a transcription factor critical for B-cell development and its genetic alterations are common in B lymphoblastic leukemia/lymphoma (B-ALL). We report a case of PAX5 P80R mutated acute leukemia with predominantly monocytic immunophenotype followed by a genetically-related histiocytic proliferation. Methods/Case Report A 27-year-old male presented with pancytopenia, epistaxis, and blurry vision. Bone marrow exam showed 95% blasts with nuclear indentations, occasional prominent nucleoli and basophilic cytoplasm. Blasts were positive for bright CD33, HLA-DR, CD14, bright CD64, partial CD123 and partial CD19. In addition, a minute population of B lymphoblasts positive for CD19, CD20, and dim TdT was seen. The AML FISH panel showed markedly aneuploid population with all probes demonstrating 3 to 5 signals. PAX5 P80R and KRAS G13D mutations were detected by NGS. Post induction bone marrow showed no evidence of acute leukemia with normal cytogenetics and FISH results. Subsequent two bone marrow exams performed due to progressive cytopenias demonstrated a prominent histiocytic proliferation with sheets of mature appearing histiocytes with abundant cytoplasm, oval to folded nuclei and occasional hemophagocytosis. This population was positive for CD163, CD14, CD68R, CD68, cyclin D1 with variable OCT2 expression and low proliferative activity. PAX5 P80R and KRAS G13D were detected. AML FISH panel showed aneuploidy in histiocytic appearing cells and IgH gene rearrangement studies by PCR showed prominent clonal population. The patient remained pancytopenic and died of disseminated fungal infection. Results (if a Case Study enter NA) NA Conclusion PAX5 P80R mutation has been primarily reported in B-ALL and is exceedingly rare in acute myeloid leukemias. This alteration has been linked to downregulation of B-cell lineage genes affecting B-cell maturation, and not surprisingly a proportion of PAX5 P80R mutated B-ALL cases show a switch to a monocytic lineage. The reported case demonstrates diagnostic caveats including unusual features of acute leukemia at the time of initial diagnosis and subsequent genetically-related histiocytic proliferation.

Surgery to Remove Adrenocortical Oncocytic Carcinoma from an Asian Male with Scoliosis

Background: Adrenocortical oncocytoma is a rare type of adrenocortical carcinoma. Its clinical characteristics and biological behaviour need to be further evaluated after the accumulation of cases.Case presentation: We report a case of adrenocortical oncocytic carcinoma in an Asian male with scoliosis. We performed an operation on this patient. Because the patient's scoliosis was limited during the operation and the tumor protruded into the chest, we decided to adopt open surgery in the supine position. During the operation, we found a tumor about 8 cm in diameter in the right adrenal region. There was local adhesion with the surrounding tissues. The surface blood vessels of the tumor were distended. After careful dissection and ligation of the blood vessels around the tumor, the adrenal tumor was completely dissociated and removed. The patient recovered well, and his hypertension was controlled after surgery. Pathological results confirmed the diagnosis of adrenocortical oncocytic carcinoma. Pathological features showed that the tumor cells were arranged in nests, with pathological mitosis, abundant cytoplasm, eosinophilia, and invasion of adipose tissue. Immunohistochemistry showed that Ki67 index was more than 15%. Conclusions: The incidence rate of eosinophilic adrenocortical carcinoma is very low. CT scans and other imaging examination methods are not specific. For larger adrenal tumors, the diagnosis of this disease should be considered. For patients with adrenal cortical carcinoma who have not yet metastasized, we can achieve sound treatment effects and reduce recurrence by removing the tumor, retroperitoneal fat around the tumor and locoregional lymph nodes.

Diagnostic approach in TFE3-rearranged renal cell carcinoma: a multi-institutional international survey

Transcription factor E3-rearranged renal cell carcinoma (TFE3-RCC) has heterogenous morphologic and immunohistochemical (IHC) features.131 pathologists with genitourinary expertise were invited in an online survey containing 23 questions assessing their experience on TFE3-RCC diagnostic work-up.Fifty (38%) participants completed the survey. 46 of 50 participants reported multiple patterns, most commonly papillary pattern (almost always 9/46, 19.5%; frequently 29/46, 63%). Large epithelioid cells with abundant cytoplasm were the most encountered cytologic feature, with either clear (almost always 10/50, 20%; frequently 34/50, 68%) or eosinophilic (almost always 4/49, 8%; frequently 28/49, 57%) cytology. Strong (3+) or diffuse (>75% of tumour cells) nuclear TFE3 IHC expression was considered diagnostic by 13/46 (28%) and 12/47 (26%) participants, respectively. Main TFE3 IHC issues were the low specificity (16/42, 38%), unreliable staining performance (15/42, 36%) and background staining (12/42, 29%). Most preferred IHC assays other than TFE3, cathepsin K and pancytokeratin were melan A (44/50, 88%), HMB45 (43/50, 86%), carbonic anhydrase IX (41/50, 82%) and CK7 (32/50, 64%). Cut-off for positive TFE3 fluorescent in situ hybridisation (FISH) was preferably 10% (9/50, 18%), although significant variation in cut-off values was present. 23/48 (48%) participants required TFE3 FISH testing to confirm TFE3-RCC regardless of the histomorphologic and IHC assessment. 28/50 (56%) participants would request additional molecular studies other than FISH assay in selected cases, whereas 3/50 participants use additional molecular cases in all cases when TFE3-RCC is in the differential.Optimal diagnostic approach on TFE3-RCC is impacted by IHC and/or FISH assay preferences as well as their conflicting interpretation methods.

Adult tissue-resident stem cells—fact or fiction?

Life-long tissue homeostasis of adult tissues is supposedly maintained by the resident stem cells. These stem cells are quiescent in nature and rarely divide to self-renew and give rise to tissue-specific “progenitors” (lineage-restricted and tissue-committed) which divide rapidly and differentiate into tissue-specific cell types. However, it has proved difficult to isolate these quiescent stem cells as a physical entity. Recent single-cell RNAseq studies on several adult tissues including ovary, prostate, and cardiac tissues have not been able to detect stem cells. Thus, it has been postulated that adult cells dedifferentiate to stem-like state to ensure regeneration and can be defined as cells capable to replace lost cells through mitosis. This idea challenges basic paradigm of development biology regarding plasticity that a cell enters point of no return once it initiates differentiation. The underlying reason for this dilemma is that we are putting stem cells and somatic cells together while processing for various studies. Stem cells and adult mature cell types are distinct entities; stem cells are quiescent, small in size, and with minimal organelles whereas the mature cells are metabolically active and have multiple organelles lying in abundant cytoplasm. As a result, they do not pellet down together when centrifuged at 100–350g. At this speed, mature cells get collected but stem cells remain buoyant and can be pelleted by centrifuging at 1000g. Thus, inability to detect stem cells in recently published single-cell RNAseq studies is because the stem cells were unknowingly discarded while processing and were never subjected to RNAseq. This needs to be kept in mind before proposing to redefine adult stem cells.

Thalamic Melanosis in Goats

Background: Melanosis is a blackened pigmentation resulting from the accumulation of melanocytes in tissues that are not normally pigmented. This change in the color of the organs occurs due to the agglomeration of melanocytes originating from abnormal migration during embryogenesis and does not cause dysfunction to the affected organ. Although melanosis frequently occurs in several species and affects several organs such as the brain and spinal cord leptomeninges, involvement in the thalamus region is unusual. The objective of this work was to report two cases of thalamic melanosis in goats, determining the pathological and histochemical aspects that assist in the diagnosis of this condition.Cases: Two cases of thalamic melanosis in goats were diagnosed. In both cases, the animals had no nervous history disease and clinical signs. The cause of death in cases 1 and 2 was established based on anatomopathological findings and clinical signs being diagnosed with mycoplasmosis and asphyxia, respectively. After fixing and making cross-sections of the brain, a focal lengthy blackened area was observed on the thalamus surface in both cases. Microscopically, lesions in the brain were similar in both cases and exclusively affected the thalamus. These cells had abundant cytoplasm, well delimited with brownish granular pigment. The nuclei were difficult to visualize and in some cells, it was rounded, well-defined, morphologically compatible with melanocytes. Melanocytes were mainly distributed around neurons and often distended the perivascular space of multiple blood vessels. In Fontana Masson staining, the granules in the cytoplasm of these cells stained strongly black. The Prussian Blue, Periodic Acid- Schiff's, Von Kossa, and Giemsa stains were negative, and the pigment remained brown. In the unstained slides, assembled after the deparaffinization and clarification process, it was observed the permanence of cells with blackish-brown pigment in the cytoplasm. In immunohistochemistry, strong immunostaining of pigmented cells with the Anti-MelanA antibodies was observed in both cases.Discussion: The diagnosis of thalamic melanosis in goats was carried out based on the characteristic pathological findings, in which melanin pigments were demonstrated and identified through HE, Fontana-Masson staining, and unstained slides and confirmed by the IHC. The use of complementary histochemical techniques was fundamental for the classification of the pigment as melanin, demonstrating to be an accessible and reliable tool for the diagnosis of pathological processes that lead to the accumulation of pigments and or material in the tissues. The occurrence of melanin in the thalamus may be associated with a failure in the migration of melanoblasts, which would go to the optical pathways or to the thalamus. This erratic migration of melanoblasts can be explained by the fact that the forebrain is the embryogenic origin of the optic and diencephalon pathways. Macroscopically, thalamic melanosis must be differentiated mainly from neoplastic processes such as melanoma and hemangiosarcoma, pigmented fungus infections, Phalaris angusta poisoning, listeriosis, neurocutaneous melanosis, and neuromelanin. It was concluded that thalamic melanosis is an uncommon alteration in goats and although it has been diagnosed as an incidental necropsy finding, should be included in the differential diagnosis of diseases that affect the central nervous system, especially those that have a color change associated with the deposition of pigments in the tissues. Keywords: melanin, necropsy findings, pigment, thalamus.Descritores: melanina, achados de necropsia, pigmento, tálamo.Título: Melanose talâmica em caprinos.

Pigmented Ependymoma of the Fourth Ventricle—A Curious Entity: Report of a Rare Case With Review of Literature

A 16-year-old boy presented with a tumor located in fourth ventricle, which showed histological features of an ependymoma replete with perivascular pseudorosettes and true ependymal rosettes. Interestingly, many of the tumor cells exhibited abundant cytoplasm stuffed with a grayish brown pigment. Histochemical stains showed the pigment to be acid fast and periodic acid–Schiff positive and negative for Masson-Fontana melanin stain. Additionally, the pigment displayed brilliant autofluorescence under ultraviolet light of a fluorescent microscope. Ultrastructure examination of the pigment revealed a non–membrane-bound biphasic structure with an electron-dense core and electron-lucent periphery. Only few similar case reports mention such pigmented ependymomas to contain a mixture of neuromelanin and lipofuscin while others mention it to be melanin itself. Our workup suggests the pigment to represent lipofuscin or its derivative. Generally known to be a pigment of wear and tear, the significance of finding it in a tumor with such abundance remains to be understood and explored.

Giant Cell Sarcomas in Domestic Rabbits (Oryctolagus cuniculus)

Multinucleated giant cells (MGCs) are a prominent histological feature of various mesenchymal neoplasms and are often considered a criterion of malignancy. Mesenchymal neoplasms with MGCs for which the cell lineage is unclear generally are referred to as giant cell sarcomas. Here we characterize the gross, histologic, and immunohistochemical features of 90 giant cell sarcomas in domestic pet rabbits. Based on the anatomic location and histologic and immunohistochemical findings, 18 cases were classified as histiocytic sarcomas (HS) and 72 cases as anaplastic sarcomas (AS). At postmortem examination, HS was either localized HS ( n = 7) always affecting the lungs, or disseminated HS ( n = 10) that affected the lungs ( n = 10), liver ( n = 6), kidneys ( n = 4), pleura ( n = 2), mediastinum ( n = 2), heart ( n = 4), skeletal muscle ( n = 1), adipose tissue ( n = 1), and lymph node ( n = 1). Additionally, one cecal biopsy was consistent with HS. Microscopically, HS were characterized by sheets of neoplastic polygonal to round cells that contained single to several, often greatly enlarged nuclei as well as abundant cytoplasm. HS were always positive for CD204 and always negative for SMA and desmin. In contrast, AS arose most commonly from the skin or subcutis ( n = 62) and rarely the skeletal muscle ( n = 8) or abdominal organs ( n = 2). In 29% of extra-abdominal AS, the tumor deeply invaded into surrounding connective tissue, skeletal muscle, tendons, and bone causing pathological fractures. Five of 9 postmortem cases metastasized to various organs often including the lungs. Microscopically, AS were characterized by sheets of spindle or pleomorphic cells admixed with variable numbers of MGCs. Immunohistochemically, AS were always negative for CD204 and often (71%) positive for SMA and/or desmin.

Rare Testicular Neoplasm: Melanotic Neuroectodermal Tumor of Infancy

We report the case of an 18-month-old boy who presented with a several-week history of left testicular swelling. On physical examination, the testicle was firm, enlarged, and nontender to palpation. The patient’s urinary habits and family history were unremarkable. An ultrasound was performed that revealed an enlarged left testis (4.7 cm) with a hypervascular heterogeneous appearance and scattered echogenic foci that raised concern for a neoplastic process. Microlithiasis was identified in the right testis (1.6 cm). AFP and hCG were within normal limits, and LDH was mildly elevated. An orchiectomy was performed and gross dissection revealed a 4.5 × 3.5 × 3.0-cm mass. The tumor was biphasic and composed of a population of poorly differentiated small round blue cells (neuroblastoma-like) and a separate component of nested epithelioid cells that had abundant cytoplasm with melanotic granules. Mitotic and karyorrhectic figures were scattered throughout. Epididymis infiltration was present. The epithelioid cells were pan-cytokeratin, EMA, and HMB-45 positive. The small round blue cells were positive for synaptophysin, vimentin, and CD117. A subpopulation was also moderately positive for CD99. A Phox2B and TDT were negative in the tumor cells, which helped to exclude neuroblastoma and lymphoma. The combined features of this case were diagnostic for melanotic neuroectodermal tumor of infancy (MNTI). This is a rare tumor with a strong predilection for the head and neck region with testicular/paratesticular localization accounting for less than 5% of MNTI cases. MNTIs are classically seen in infants under 1 year of age and typically behave in a benign fashion, although metastases to retroperitoneal lymph nodes and lymphatics have been documented. It is important to remember the differential of pediatric testicular neoplasms as it can mimic other small round blue cell tumors.