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Pulmonary hamartoma (PH) may show various combinations of mesenchymal tissues with entrapment of respiratory epithelium. An uncommon variant of PH prevalently consisting of smooth muscle with mucinous proliferation has been reported in literature under several definitions as sporadic reports. We collected a series of 6 leiomyomatous PH associated with mucinous growth from consultation files (3 cases) and multicentric revision of archival files among 128 consecutive surgically resected PH. The lesions have a prevalence for male gender (5:1) and lower lobes (5:1), with a mean age at diagnosis of 61 years. All cases were incidentally disclosed in asymptomatic patients and had an indolent behavior. At histology, 2 cases consisted uniquely of smooth muscle and 4 also showed mature adipose tissue. The mucinous proliferation consisted of a monotonous growth of columnar cells lacking p63-positive basal cells and expressing pan-CKs, MUC5A, and CK7, but negative with TTF-1, napsin, MUC1, MUC2, MUC6, CK20, and CDX2. Smooth muscle was negative with hormonal receptors. Molecular analysis using a multiplex gene panel did not reveal gene mutations, while ALK, BRAF, and ROS1 were negative. In conclusion, we describe a small series of uncommon PH with prevalent leiomyomatous mesenchymal component associated with a mucinous growth (mucinous adenomyomatous hamartoma). Despite the lack of basal cells coating mucinous proliferation and irregular architecture, the favorable outcome and lack of molecular alterations most likely lay for a benign/low-grade tumor. Pathologists should be aware of this unusual occurrence to prevent a diagnosis of overt malignancy, particularly in frozen section, small biopsy, and cytology.

The pathologist is frequently involved in the diagnostic approach to the patient with suspected sarcoidosis. Although the histologic diagnosis is generally not difficult, atypical and underrecognized features may occasionally occur and may result in diagnostic problems. The authors review the histology of pulmonary sarcoidosis, focusing particularly on these unusual problematic findings.

We report a rare case of malignant pleural mesotheliomapresentingclinically with pneumotho ax and histologically with an exclusiveintrapulmonary lepidic growth. Neither intrathoracic nodules norpleural thickening were found. The patient subsequently experiencedacute abdominal painwith peritonitis and intestinal occlusion byperitoneal mesothelioma. The morphologic clues leading to the correct diagnosis of mesothelioma with prominent intrapulmonary growth are briefly discussed.

Primary renal lymphomas are very rare, and primary kidney-limited lymphomas with cystic presentation have never been described before. This study reports a case of diffuse large B-cell lymphoma associated with chronic inflammation occurring in a renal pseudocyst: an infrequent neoplasm with an unusual and subtle clinical presentation.