Pituitary adenoma (PA) is a common benign neuroendocrine tumor; however, the incidence and proportion of hormone-producing PAs in Korean patients remain unknown. Authors analyzed 506 surgically resected and pathologically proven pituitary lesions of the Seoul National University Hospital from 2006 to 2011. The lesions were categorized as: PAs (n = 422, 83.4%), Rathke's cleft cysts (RCCs) (n = 54, 10.6%), inflammatory lesions (n = 8, 1.6%), meningiomas (n = 4), craniopharyngiomas (n = 4), granular cell tumors (n = 1), metastatic renal cell carcinomas (n = 2), germinomas (n = 1), ependymomas (n = 1), and unsatisfactory specimens (n = 9, 1.8%). PAs were slightly more prevalent in women (M: F = 1:1.17) with a mean age of 48.8 yr (9-80 yr). Immunohistochemical analysis revealed that prolactin-producing PAs (16.6%) and growth hormone-producing adenomas (9.2%) were the most common functional PAs. Plurihormonal PAs and nonfunctioning (null cell) adenomas were found in 14.9% and 42.4% of patients with PAs, respectively. The recurrence rate of PAs was 11.1%, but nearly 0% for the remaining benign lesions such as RCCs. 25.4% of patients with PAs were treated by gamma-knife after surgery due to residual tumors or regrowth of residual tumor. In conclusion, the pituitary lesions and the proportions of hormone-producing PAs in Korean patients are similar to those of previous reports except nonfunctioning (null cell) PAs, which are unusually frequent.Graphical Abstract

Pilomatricoma is a benign tumor arising from the primitive basal cells of the epidermis that differentiate into hair matrix cells. Mutations in the CTNNB1 gene, which encodes β-catenin (a protein involved in hair growth), play an etiological role in the development of pilomatricoma. A 34-yearold woman presenting with a mass in the right parotid region underwent an excisional biopsy. The mass was conclusively diagnosed as pilomatricoma. During pregnancy, the mass grew from 1 cm to 5 cm in diameter and was accompanied by pain and tenderness. The growth may have been facilitated by the increased production of estrogen and progesterone, which bind to receptors located in the outer root sheath cells of the hair follicles. No recurrence was observed during 6 months of follow-up.

We report the first case of a 62‐year‐old man with a sclerosing pneumocytoma (SP) combined with a typical carcinoid (TC) and pulmonary adenocarcinoma in different lung lobes. Computed tomography revealed two nodules. The radiological diagnosis was primary lung cancer and a metastatic nodule; however, no enlarged lymph nodes were observed. Histological and immunohistochemical analyses defined the 1.7 cm nodule in the right upper lobe as adenocarcinoma and the 1.3 cm nodule in the left lower lobe as SP combined with TC. This case is noteworthy because of the rarity of SP combined with TC, the comprehensive examination of frozen and permanent sections, and the clinical implications of the differential diagnosis of lung nodules.

Chordomas are rare, locally aggressive bone malignancies with poor prognoses. However, those with minimal or no bone involvement are more easily resectable because of their well-delineated margins and thus have better prognoses. Such extraosseous chordomas of the spine are localized both intradurally and extradurally. Only a few case reports have focused on extraosseous, extradural spinal chordomas. Radiologically, this type of chordoma has a dumbbell shape; however, dumbbell-shaped spinal tumors are traditionally thought to be neurogenic tumors (i.e., schwannomas or neurofibromas). We herein report a unique case involving a woman with a dumbbell-shaped extraosseous chordoma protruding predominantly into the retropharyngeal space. A 44-year-old woman presented for evaluation of a left submandibular mass. A T2-hyperintense, gadolinium-enhancing mass was found in her cervical spinal canal, protruding through the C2/3 neural foramen into the retropharyngeal space with minimal vertebral involvement. The initial diagnosis was a neurogenic tumor, most likely a schwannoma. After subtotal removal, the pathologic diagnosis was a chordoma. Because chordomas and schwannomas have significantly different prognoses, caution is warranted when a dumbbell-shaped tumor is identified in the spine with minimal or no vertebral deterioration on radiology. This report also provides the first thorough review of extraosseous dumbbell-shaped intraspinal–extraspinal chordomas.

Nuclear protein in testis (NUT) carcinoma is a rare, aggressive carcinoma that is a diagnostic challenge for pathologists. Here, we report a case of NUT carcinoma in a 63-year-old woman with uncommon immunohistochemical results. The initial bronchoscopic biopsy revealed a poorly differentiated carcinoma with p63 immunohistochemical stain positivity. However, the cytomorphological features of the pleural fluid were unusual. Immunohistochemical staining of the pleural fluid revealed diffuse positivity for vimentin and focal positivity for cytokeratin and neuroendocrine markers. Because of chemoresistance, other malignancies, including sarcomatoid carcinoma, combined small cell carcinoma, and an unusual form of NUT carcinoma, were considered as differential diagnoses. The diagnosis of NUT carcinoma was confirmed using NUT-specific antibodies and fluorescence in situ hybridization. The current case was a diagnostic challenge because of the poorly differentiated cytomorphology and uncommon immunohistochemical results. Pathologists and clinicians should consider NUT carcinoma in the differential diagnosis, as this malignancy has a dismal prognosis and needs to be diagnosed accurately for the most effective treatment. Key points:• Metastatic NUT carcinoma can show diffuse vimentin positivity and focal neuroendocrine marker positivity. NUT carcinoma can be misdiagnosed as basaloid squamous cell carcinoma in routine diagnosis, especially in older-aged patients. • This study was a diagnostic challenge because of the poorly differentiated cytomorphology and uncommon immunohistochemical results for NUT carcinoma. Pathologists should differentially diagnose NUT carcinoma when rare cytohistological features are observed at any age.