A 60-year-old male presented with a history of a relatively hard and cystic right chest mass that had gradually increased in size, with subsequent skin erosion, exudate and hemorrhage. The cytologic specimens from a cyst fluid contained a large number of sheet-like or papillary clusters of atypical cuboidal to columnar epithelial cells with loss of myoepithelial components, in a severely inflammatory background with scattered siderophages. We first interpreted it as a carcinoma, but could not completely exclude out the possibilities of benign. Tumor extirpation was performed, and a gross examination of the neoplasm revealed a giant, cystic and partly solid papillary-projected tumor lesion, with a gray-whitish cut surface, associated focally with skin invasion, measuring approximately 9 × 7 cm with a 6 × 4 cm solid area in diameter. On a microscopic examination, solid parts of the tumor were predominantly composed of the intracystic proliferation of mildly atypical epithelial cells with absence of two-cell patterns in a papillary or papillotubular growth fashion, only partly involving the dermis to epidermis. Immunohistochemistry showed that the carcinoma cells were specifically positive for estrogen and progesterone receptors, whereas negative for p63, S-100 protein and several neuroendocrine markers. Therefore, we finally made a diagnosis of invasive intracystic carcinoma of the male breast. We should be aware that owing to its characteristic cytological features, cytopathologists might be able to make a correct diagnosis of that, based on multiple and adequate samplings, even though a core biopsy would be the absolute minimum assessment.

Background Intravascular papillary endothelial hyperplasia (IPEH) is a reactive lesion histopathologically characterized by papillary growth of vascular endothelial cells. IPEH is most commonly found in the skin and subcutaneous tissues of the head, neck, and extremities. Furthermore, it has been reported to occur in oral surgery, but its occurrence in bone is extremely rare. Case Presentation We present the case of a 77‐year‐old man with a chief complaint of left knee arthralgia. The knee joint X‐ray showed Kellgren–Lawrence grade 4 osteoarthritis and a mass lesion with decreased permeability within the bone in the medial part of the proximal tibia. Computerized tomography (CT) scan of the left knee showed a localized mass in the left proximal tibia with clear margins and granular internal calcification. The preoperative diagnosis was left knee osteoarthritis and a benign tumor of the left proximal tibia (enchondroma or hemangioma). The patient requested surgical treatment, so left total knee arthroplasty (TKA) and resection of the tumor were performed. The pathology revealed a rare intraosseous IPEH with marked calcification. Conclusions Since intraosseous IPEH could not be considered from the clinical findings, the pathological diagnosis was the decisive factor. This report showed the world's first case of intraosseous IPEH with marked calcification. Similar to the calcification of intraosseous hemangiomas, we considered the possibility that, in IPEH, the thrombus may fibrosis and organize in concentric circles, causing necrosis at the center and resulting in calcification. TKA was performed on the degenerative knee joint with IPEH, and a good patient outcome was obtained.