Endocrine Abstracts (2017) 50 EP044 | DOI: 10.1530/endoabs.50.EP044

Investigating an isolated serum alkaline phosphatase: an incidental mediastinal seminoma

Parizad Avari1, Kavita Shapriya2, Gordon Rustin3 & Ana Pokrajac2


1Northwick Park Hospital, London North West Healthcare NHS Trust, London, UK; 2Watford General Hospital, West Hertfordshire Hospitals NHS Trust, Watford, UK; 3Mount Vernon Hospital, The Hillingdon Hospitals NHS Foundation Trust, Northwood, UK.


Serum alkaline phophatase (ALP) may be released from various sources, including liver, bone, thyroid, intestine and placenta. Herein, we describe a rare case of an isolated serum ALP rise initially dismissed, and later resulting in an incidental finding of a mediastinal seminoma.

A 56-year-old gentleman was referred to the Endocrinology Outpatients by his general practitioner, with a 1-month history of presumed post-viral fatigue and rise in serum ALP. He was initially investigated by the Gastroenterologists for two benign liver cysts, with no interval change on imaging. The patient was thereafter discharged.

Subsequent endocrine investigations revealed mildly low Vitamin-D at 55 nmol/L, ESR 45 mm/hour, IgG 17.2 g/dL and IgM 2.45 g/dL with slight polyclonal increase in gamma region. Autoimmune, thyroid and pituitary profile normal. A further rising ALP prompted a skeletal survey, which showed no bony lesions, but an anterior mediastinal mass 15.6 cm×8.6 cm x14 cm encasing at least two-thirds of the circumference of the ascending aorta. No other significant lesions were found on staging CT. Diagnostic core biopsy was in keeping with a seminoma, associated with strongly, diffuse positive placental ALP (PLAP), and positive CD5 and CD45.

Differential diagnosis of a mediastinal mass in the context of an isolated ALP rise, include thymoma, lymphoma and teratoma. Less than 5-7% of germ cell tumours are extragonadal, but often respond well to radio/chemo-therapy. The patient in our case underwent neoadjuvant chemotherapy and surgery, remaining disease free thereafter. Prompt diagnosis is therefore paramount to minimise complications.

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