Clear Cell Tumors of Soft Tissue

Soft Tissue Perivascular Epithelioid Cell Tumors

Perivascular epithelioid cell tumors (PEComas) are a heterogenous group of mesenchymal neoplasms with a mixed myomelanocytic immunophenotype. PEComa-family tumors include angiomyolipoma, lymphangioleiomyomatosis, and a large category of rare neoplasms throughout the body that are now classified under the umbrella term "PEComa." This review focuses on recent advances in the clinicopathological and molecular features of PEComas, with an emphasis on PEComas that originate in soft tissue.

Mesenchymal tumours with melanocytic expression: a potential pitfall in the differential diagnosis of malignant melanoma

Mesenchymal tumours with melanocytic expression can pose a diagnostic challenge because they frequently demonstrate both morphological and immunohistochemical overlap with other cutaneous melanocytic neoplasms. Therefore, they present potential pathological pitfalls that may lead to a misdiagnosis of malignant melanoma. Mesenchymal neoplasms that closely mimic melanoma include malignant melanotic nerve sheath tumour (melanotic schwannoma), epithelioid schwannoma, malignant peripheral nerve sheath, cutaneous syncytial myoepithelioma, clear cell sarcoma of soft tissue, and perivascular epithelioid cell tumour. Awareness of these melanoma mimics is necessary for establishing the correct diagnosis so that the appropriate clinical management can be rendered to the patient. This in-depth review highlights key diagnostic features and molecular genetics and also discusses the differential diagnosis and treatment of mesenchymal tumours that exhibit melanocytic expression.

Perivascular Epithelioid Cell Tumor (PEComa) of the Lung in a 56-Year-Old Female Patient: A Case Report

Perivascular epithelioid cell tumors, best known as PEComas, are extremely uncommon mesenchymal tumors The etiology of PEComas remains unestablished and its clinical presentation is usually benign. PEComas lack a distinctive symptomatic presentation; thus, the diagnosis of these tumors relies mainly on pathological examinations. These neoplasms have a very distinct immunoreactivity for melanocytic markers critical for their identification. Due to the rarity of these tumors and lack of a distinct disease presentation, we discuss the diagnostic relevance of imaging and pathologic findings in a 56-year-old woman diagnosed with a PEComa in the right middle lobe of the lung.

Clear cell lesions in pathology: Histomorphologic approach to diagnosis

There has been remarkable progress in the field of surgical pathology; however, histomorphology has remained the most important and essential tool of the surgical pathologist in everyday practice till now. It is surprising that the hematoxylin-eosin (H and E) stain, introduced more than a century ago, has still remained the gold standard stain for histological examination and diagnosis of human diseases. Besides different findings or clues observed in histopathology sections like inclusions, granules, grooving, globules, halo, or clearing, which would enable the pathologist to provide a precise and accurate diagnosis; observation of clear cells is one of the important findings and clue for reporting. It may also sometimes lead to difficulties and delays in establishing the diagnosis. It can be focal or extensive and primary or rarely it may be secondary. Clear cell changes may be observed in many non-neoplastic, benign, or malignant tumors of diverse origin. Clear cell tumors contain a preponderance of clear cells. It can be seen in almost all the organs of human body and can be classified according to location or biological behavior. Commonly seen clear-cell tumors are usually malignant and common organs involved are female genital tract, urogenital tract, head and neck areas, central nervous system, skin, and rarely in bone and soft tissues. For approach to clear cell lesions, one has to decide if the change is artifactual, a mimic of clear cell tumors, or a clear cell tumor in reality. Once the mimics and artifactual/degenerative changes have been ruled out, a tumor either primarily of clear cell origin or showing secondary change has to be decided. The tumor next is to be diagnosed as benign/malignant and epithelial/mesenchymal based on morphology.

Perivascular epithelioid cell tumour of the bladder

A 39-year-old woman presented with a long history of pelvic pain and urinary urgency. Prior workup by her primary care doctor had been negative. The patient's gynaecologist ultimately referred her to a urologist following an ultrasound that revealed a possible bladder mass. MRI of the abdomen and pelvis demonstrated a 4 cm soft tissue lesion arising from the bladder. Cystoscopy showed an atypical mass on the anterior bladder wall, and pathological examination of the TURBT (transurethral resection of the bladder tumour) specimen revealed a perivascular epithelioid cell tumour (PEComa) with involvement of the detrusor muscle. The patient underwent a robotically assisted laparoscopic partial cystectomy. Final pathology confirmed a PEComa with negative margins. The patient had an uncomplicated postoperative course and is doing well following surgery. A surveillance cystoscopy at 6 months showed no evidence of recurrence. This case underscores the variability of clinical presentation of PEComas while proposing an appropriate method of surgical management.