Progressive supranuclear palsy (PSP) is a disease of later life that is currently regarded as a form of neurodegenerative tauopathy. Disturbance of gaze is a cardinal clinical feature of PSP that often helps clinicians to establish the diagnosis. Since the neurobiology of gaze control is now well understood, it is possible to use eye movements as investigational tools to understand aspects of the pathogenesis of PSP. In this review, we summarize each disorder of gaze control that occurs in PSP, drawing on our studies of 50 patients, and on reports from other laboratories that have measured the disturbances of eye movements. When these gaze disorders are approached by considering each functional class of eye movements and its neurobiological basis, a distinct pattern of eye movement deficits emerges that provides insight into the pathogenesis of PSP. Although some aspects of all forms of eye movements are affected in PSP, the predominant defects concern vertical saccades (slow and hypometric, both up and down), impaired vergence, and inability to modulate the linear vestibulo-ocular reflex appropriately for viewing distance. These vertical and vergence eye movements habitually work in concert to enable visuomotor skills that are important during locomotion with the hands free. Taken with the prominent early feature of falls, these findings suggest that PSP tauopathy impairs a recently evolved neural system concerned with bipedal locomotion in an erect posture and frequent gaze shifts between the distant environment and proximate hands. This approach provides a conceptual framework that can be used to address the nosological challenge posed by overlapping clinical and neuropathological features of neurodegenerative tauopathies.

Background Sarcomas are uncommon findings in body cavity fluids. Diagnosis may be challenging because sarcoma cells in fluids can round up and lose their characteristic appearance seen on smears and histologic sections. This study characterizes the cytologic features of sarcomas involving body cavity fluids. Methods Effusion fluids and cerebrospinal fluids diagnosed as positive for sarcoma were reviewed. Results Forty‐three fluids from 28 patients (median age, 47 years) were positive for sarcoma. Four patients who presented with positive fluids were alive at 1 to 10.7 years' follow‐up (median, 22.5 months). Twenty‐four patients died 2 days to 2 years (median, 19 days) after their positive fluid diagnoses. Twenty‐eight specimens from 20 patients had slides available for review. Although 18 of the 28 positive fluids had a morphology comparable to that of their primary, 4 small round blue cell tumors (SRBCTs) and 4 spindle cell tumors showed epithelioid morphology, 1 SRBCT had pleomorphic morphology, and 1 epithelioid primary had SRBCT morphology. Nine fluids had tumor cells in large, cohesive clusters mimicking carcinoma; workup was performed for 10, predominantly to rule out carcinoma and mesothelioma. Conclusions Sarcoma morphology may be altered in exfoliated cytology specimens. Workup on cell blocks aids in the differential diagnosis, especially for carcinoma and mesothelioma. Unsurprisingly, fluid cytology positive for sarcoma portends poor survival.

Aims Nuclear protein in testis (NUT) carcinoma, an aggressive tumour driven by NUTM1 rearrangements, often involves the lung/mediastinum and shows squamous differentiation. We encountered an index patient with a thoracic NUT carcinoma diagnosed by molecular testing, showing extensive pleural involvement and diffuse thyroid transcription factor‐1 (TTF‐1) expression, initially suggestive of lung adenocarcinoma with pseudomesotheliomatous growth. We thus gathered an institutional series of thoracic NUT carcinomas to examine their pathological spectrum. Methods and results We searched for thoracic NUT carcinomas in our surgical pathology files and in 2289 consecutive patients with primary thoracic tumours investigated with RNA‐based assays. We performed NUT immunohistochemistry on 425 additional lung adenocarcinomas. Collectively, we identified six patients (five men and one woman; age 31–80 years; four never‐smokers) with thoracic NUT carcinomas confirmed by molecular testing (including five with positive NUT immunohistochemistry). They died at 2.3–12.9 months (median, 2.8 months) after presentation. Two patients were diagnosed by histopathological assessment, and the remaining four (including the index patient) were diagnosed by molecular testing. Analysis of the index case revealed expression of multiple neuroendocrine markers and TTF‐1; no ultrastructural evidence of neuroendocrine differentiation was noted. No additional NUT‐positive cases were found by immunohistochemical screening. Conclusions Although NUT carcinoma classically shows squamous differentiation, it can rarely express TTF‐1 (even diffusely) and/or multiple neuroendocrine markers. This immunophenotypic spectrum may lead to diagnostic confusion with pulmonary adenocarcinoma, neuroendocrine tumour, and others. To circumvent this pitfall, NUT immunohistochemistry and/or NUTM1 molecular testing should be considered in primitive‐appearing tumours, regardless of their immunophenotypic features.