Oct. 26, 2018

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  1. Perivascular epithelioid cell lesion (PEComas) Vikram Prabhakar (DCP,DNB Pathology)
  2. • PEComas are a collection of rare tumors defined as “mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells” . • In 1991, Pea et al. described the presence of a unique cell with “prominent cytoplasmic borders and clear to granular, eosinophilic cytoplasm” in a perivascular distribution in both angiomyolipoma (AML) of the kidney and clear cell sugar tumor (CCST) of the lung .
  3. • PEComas are related to the genetic alterations of tuberous sclerosis complex (TSC), an autosomal dominant genetic disease due to losses of TSC1 (9q34) or TSC2 (16p13.3) genes which have a role in the regulation of the Rheb/mTOR/p70S6K pathway. • PEComas can occur at the extremes of age, but the median age of 43 years in • A strong female predominance has been seen ; approximately 4 : 1
  4. PEComa-NOS have been described in a variety of anatomic locations, including:-- 1. the colon 2. pancreas 3. retroperitoneum 4. heart 5. adrenal gland 6. breast 7. eye 8. biliary tract 9. bone 10. urinary bladder 11. skull base 12. liver 13. uterus cervix 14. skin 15. nasopharynx 16. upper airway 17. soft tissues
  5. • PEComs has been given a variety of titles, including:-- 1. clear cell sugar tumor 2. primary extrapulmonary sugar tumor 3. clear cell myomelanocytic tumor 4. monotypic epithelioid angiomyolipoma
  6. What is the perivascular epithelioid cell? • It has morphologic, epithelioid appearance with a clear to granular cytoplasm, a round to oval, centrally located nucleus and an inconspicuous nucleolus. PEC has mild to any atypia and a typical perivascular location . • At present, PEC has not a known normal counterpart.
  7. Immunohistochemically • PEComas express myogenic and melanocytic markers, such as HMB45, HMSA-1, MelanA/Mart1, microophtalmia transcription factor (Mitf), actin and, less commonly, desmin . • Its immunoreactivity for vimentin is usually incospicuous.
  8. ultrastructural analysis • PEC contains microfilament bundles with electron-dense condensation, numerous mithochondria and membrane-bound dense granules.
  9. Different modulations
  10. Kidney • PEComas of the kidney include :-- 1. classic AML 2. microscopic AML (so-called microhamartoma) 3. intraglomerular lesions 4. cystic AML, 5. epithelioid AML, 6. oncocytoma-like AML 7. lymphangiomyomatosis of the renal sinus.
  11. Classic angiomyolipoma • is the most common mesenchymal tumor of the kidney. • composed of a variable mixture of adipose tissue and spindle and epithelioid smooth muscle cells mixed together with abnormal thick-walled blood vessels.
  12. Renal angiomyolipoma: perivascular epithelioid cells arranged around a blood vessel
  13. Renal microhamartoma completely composed of perivascular epithelioid cells
  14. Lung • PEComas of the lung include :-- 1. Lymphangioleiomyomatosis 2. clear-cell “sugar” tumor.
  15. Lymphangioleiomyomatosis • It is a rare and progressive disease that affects women, usually in premenopausal age; occasionally • Nodular, often widespread and bilateral interstitial proliferation of HMB45, actin and desmin-positive smooth muscle cells which can vary from small spindle-shaped cells to large epithelioid cells • usually arranged around thin-walled, branching vascular channels; which is associated with dilated lymphatics and cystic changes
  16. Pulmonary lymphangioleiomyomatosis composed of epithelioid cells arranged around a vascular channel
  17. Clear cell sugar tumor • It was originally described in the lung • Rare and benign neoplasm composed of a uniform population of round-to-polygonal epithelioid cells, with a clear or eosinophilic cytoplasm and well-defined cell borders. • Tumor cells are surrounded by prominent and thin-walled vascular channels, having a nested or alveolar .
  18. Pulmonary clear-cell “sugar” tumor composed of epithelioid cells with a clear cytoplasm and well-defined cell borders. With prominent and vascular channel is present
  19. Pulmonary clear-cell “sugar” tumor: HMB45 immunoreactivity in tumor cells
  20. Liver Hepatic angiomyolipoma: solid component made of large epithelioid cells
  21. The tumor cells are strongly and diffusely immunoreactive for HMB45 (A), Melan A (B), and vimentin (C) and focally immunoreactive for α- smooth muscle actin (SMA)
  22. Pancreas Pancreatic clear-cell “sugar” tumor: epithelioid cells, with a clear cytoplasm and with a nested or appearance
  23. Uterus Uterine PEComa composed of epithelioid cells with a clear cytoplasm and well-defined cell borders
  24. Bladder Bladder PEComa composed of epithelioid cells with clear cytoplasm arranged in nests
  25. Prostate Prostatic PEComa composed of epithelioid cells with clear cytoplasm arranged in nests
  26. Differential diagnosis 1. Clear cell / oxyphilic carcinoma: cytokeratin+ 2. Epithelioid / clear cell smooth muscle tumors: HMB45- 3. Melanoma: strong S100+ 4. Undifferentiated / high grade sarcoma
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