Lung
Mesenchymal tumors
PEComa (clear cell tumor)
Author: Roseann I. Wu, M.D., M.P.H.
Last author update: 1 September 2016
Last staff update: 8 May 2023
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: PEComa clear cell tumor lung
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Radiology description | Radiology images | Prognosis and treatment | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosisCite this page: Wu R. PEComa (clear cell tumor). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungtumorclearcell.html. Accessed April 19th, 2024.
Definition / general
- Benign/borderline peripheral lung neoplasm derived from perivascular epithelioid cells
- Member of perivascular epithelioid cell tumor (PEComa) or "myomelanocytoma" family, which includes angiomyolipoma, lymphangioleiomyomatosis (LAM)
- Grouped with LAM under PEComatous tumors in 2015 WHO Classification of Lung Tumors (J Thorac Oncol 2015;10:1243)
- Sheets of large cells with clear to eosinophilic granular cytoplasm and PAS+ glycogen granules
Essential features
- Extremely rare, benign pulmonary tumor derived from perivascular epithelioid cells (PEComa family of tumors)
- Clear to eosinophilic, finely granular cytoplasm containing abundant PAS+ glycogen
- Stains with melanocytic and smooth muscle markers by immunohistochemistry
Terminology
- First described as clear cell tumor of lung but also known as sugar tumor due to intracytoplasmic glycogen (Yale J Biol Med 1971;43:213)
- Considered a benign PEComa in the lung, as opposed to malignant PEComa
ICD coding
- D14.31 Benign neoplasm of right bronchus and lung
- D14.32 Benign neoplasm of left bronchus and lung
- D14.30 Benign neoplasm of unspecified bronchus and lung
Epidemiology
- Extremely rare, case reports and small case series
- Generally older adults >40 years old, may occur in children
- No clear gender predilection
Sites
- Generally arises in peripheral lung, rarely in trachea or bronchi
Pathophysiology
- May rarely arise in patients with tuberous sclerosis along with lymphangioleiomyomatosis (LAM) and micronodular pneumocyte hyperplasia (MMPH) (Am J Surg Pathol 1997;21:1242)
Etiology
- Mesenchymal perivascular epithelioid cells (PEComa family)
Clinical features
- Generally asymptomatic or nonspecific pulmonary symptoms
Diagnosis
- Generally incidental finding on imaging
- Requires tissue diagnosis with immunohistochemistry
Radiology description
- Solitary, homogenous, rounded, circumscribed, peripheral lung mass
- Hyperintense due to vascularity
- May show FDG uptake on PET (Interact Cardiovasc Thorac Surg 2007;6:676)
Radiology images
Images hosted on other servers:
CT of clear cell tumor of lung
Prognosis and treatment
- Rare case reports of malignant features and visceral metastasis
- Aggressive features may include nuclear pleomorphism, >5 cm size, increased mitoses, necrosis (consider malignant PEComa)
Case reports
- 38 year old man with clear cell tumor of lung and liver AML (Ann Thorac Cardiovasc Surg 2014;20 Suppl:453)
- 41 year old man with rapidly growing coin lesion (Ann Thorac Surg 2011;91:588)
- 51 year old man with benign sclerosing PEComa (J Pathol Transl Med 2016;50:238)
- 60 year old man with clear cell tumor of lung with CD1a expression (Pathol Int. 2006;56:453)
- 64 year old man presenting with round pulmonary nodule (J Korean Med Sci 2008;23:1121)
- 65 year old woman with clear cell tumor of lung adjacent to visceral pleura (Gen Thorac Cardiovasc Surg 2010;58:243)
Treatment
- Simple surgical excision
Gross description
- Small (< 5 cm), sharply outlined, glistening, red-tan to brown mass, usually in peripheral lung
- Uniform cut surface, though may have foci of necrosis
Gross images
Images hosted on other servers:
Well circumscribed tumors
4 cm, gray-white, circumscribed tumor
confined to the lower lobe under the pleura
Microscopic (histologic) description
- Organoid (thick cords and rounded nests with sinusoid-type vascular network) or sheets of epithelioid cells
- Clear to eosinophilic granular cytoplasm, well defined cell borders, numerous PAS+ glycogen granules
- Small, uniform, rounded nuclei with small nucleoli, variably prominent sclerotic vasculature, may have extracellular amorphous eosinophilic material with variable calcification
- Occasionally “spider cells” with nuclear condensation of eosinophilic cytoplasm with extensions to the cell membrane
- May show entrapped small airways, necrosis, sparse lymphocytes
- No fat, no / rare mitoses
- Rarely malignant features (J Clin Oncol 2010;28:e626, Histopathology 2011;58:498)
Microscopic (histologic) images
Images hosted on other servers:
(A) Core needle biopsy shows neoplastic cells in nested and insular pattern surrounding numerous thinned wall sinusoid-like vessels
(B) intranuclear cytoplasmic invaginations
(C) HMB45+ staining
Tumor with malignant histology
Various images
Cytology description
- Small and large cohesive clusters of bland epithelioid to spindle cells with oval or elongated nuclei, indistinct nucleoli, finely vacuolated cytoplasm, delicate transgressing vessels, background naked nuclei, rare intranuclear pseudoinclusion (Diagn Cytopathol 2008;36:89)
Cytology images
Images hosted on other servers:
Benign sclerosing perivascular
epithelioid cell tumor (PEComa)
(A) Large, irregular, cohesive clusters of columnar and spindle-shaped cells in background of single naked nuclei (Pap)
(B) several large clusters with open cribriform-like spaces (Pap)
(C) spindle-shaped and polygonal cells with round to oval nuclei and vacuolated ill-defined cytoplasm (Pap)
(D) cell block shows neoplastic cells arranged in a nested and insular pattern surrounding sinusoid-like vessels; inset shows sinusoid-like vessel amidst tumor
Positive stains
- HMB45, MART1/MelanA, MITF, SMA, desmin, variable S100
- CD1a (Pathol Int 2008;58:169)
Electron microscopy description
- Hybrid features of pericytes, melanocytes, and neuroendocrine cells (Ultrastruct Pathol 2001;25:479)
- Interdigitating cell processes, primitive cell junctions, intracytoplasmic glycogen (Am J Surg Pathol 1990;14:248)
Molecular / cytogenetics description
- TSC2 loss of heterozygosity when arises in patient with tuberous sclerosis
Differential diagnosis
- Primary or metastatic carcinomas with clear cell pattern, e.g. renal cell carcinoma
- Metastatic clear cell sarcoma
- Metastatic melanoma
- Paraganglioma
