A STRANGE CAUSE OF A PULMONARY NODULE

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SESSION TITLE: Medical Student/Resident Lung Cancer Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Perivascular epithelioid cell tumors (PEComas) are part of an uncommon group of mesenchymal tumors with histological and immunohistochemical markers for myogenic and melanocytic tissue. Its prevalence is very low, accounting for approximately 100 reported cases in the literature with 20 % of them exhibiting lung metastasis. Nonspecific gynecologic symptoms appear to be the most common manifestation. The majority of these cases are classified as non-malignant, thus making our case very atypical. Given that these tumors are extremely rare, there are no specific therapeutic guidelines in the literature. Some experts recommend tumoral resection and adjuvant chemotherapy or radiotherapy in malignant cases. CASE PRESENTATION: We describe a 62-year-old nulligravid female with no known past medical history who came to the emergency room with suprapubic discomfort of one-day evolution. An abdominopelvic computed tomography (CT) revealed a large pelvic mass of 27 cm x 19 cm x 22 cm with heterogeneous density and calcifications, ascites, as well as bibasilar pulmonary nodules. A subsequent chest CT scan showed the presence of multiple bilateral nodular lesions, the largest one measuring 3.6cm x 2.6 cm. Histological sampling was obtained via CT guided biopsy from lung and uterus which came back positive for HMB45, CD10, and for desmin consistent with a metastatic malignant PEComa of gynecologic origin. The patient underwent pelvic mass surgical resection and at the moment is receiving mTOR inhibitors. DISCUSSION: This extremely rare type of tumor is immunoreactive for smooth muscle and melanocytic markers. Its behavior is marked by invasion of the vessel wall and smooth muscle. While some PEComas occur in patients with tuberous sclerosis, it’s lack of association often leads to an inverse relation of malignant potential. Proposed guidelines for classification of PEComas divide them into benign, uncertain malignant potential and malignant. In view of the low prevalence of PEComas, treatment options are limited and prognostic factors are uncertain. Several case studies have discussed the benefit of mTOR inhibitors, chemotherapy, and radiotherapy. Initial therapy with mTOR inhibitors seems to be the best approach while disease progression allows. CONCLUSIONS: PEComas are an extremely rare type of sarcoma very rarely showing metastasis. Typical symptoms can be nonspecific and diverse given organ involvement. PEComa must be kept in the differential diagnosis of gynecological tumors despite its low prevalence. All PEComas exhibit both melanocytic (HMB45, Melan-A, tyrosinase, microphthalmia transcription factor) and myoid (desmin, smooth muscle actin, muscle-specific actin, caldesmon, calponin) markers. Treatment strategies include tumor resection and a combination of mTOR inhibitors, chemotherapy or radiation. Lung nodularities may represent metastasis and in appropriate setting may lead to diagnosis. Reference #1: Henry B Armah; Anil V Parwani. Malignant perivascular epithelioid cell tumor (PEComa) of the uterus with late renal and pulmonary metastases: a case report with review of the literatura. Diagnostic Pathology 2, Article number: 45 (2007) Reference #2: Valentina Natella; et al. A huge malignant perivascular epithelioid cell tumor (PEComa) of the uterine cervix and vagina. Pathology - Research and Practice, Volume 210, Issue 3 (2014) Reference #3: Óscar Cuevas Herreros;Lilian Escobar Lezcano; Manuel Rodriguez Blaco; Vicente Artigas Raventós. PEComa, un raro tumor de células epiteliodes. Cirugia Española.Vol 93. Num. 7. 65-67 (2015) DISCLOSURES: no disclosure on file for Rosangela Fernandez-Medero; No relevant relationships by Juan Garcia-Puebla, source=Web Response No relevant relationships by Ricardo Hernandez, source=Web Response No relevant relationships by Kimberly Padilla Rodriguez, source=Web Response no disclosure on file for Ileana Rivera Burgos; No relevant relationships by Gabriela Torres, source=Web Response No relevant relationships by Marina Torres Torres, source=Web Response