Thymic mucinous adenocarcinoma

There have been two case reports of mucinous (colloid) adenocarcinoma of the thymus, in a 15 year old boy1 and a 59 year old man2.

Histopathology

The tumour in the adult showed an acinar and cribriform architecture of tall columnar cells, with varying amounts of cytoplasmic mucin2.

Immunohistochemistry

	CD5	1/1(focal and weak)1, 1/1(focal)2
	34bE12	0/11, 1/12
	CK5/6	0/11, 0/12
	CK7	1/1(focal)1, 1/1(diffuse)2
	CK20	1/1(focal)1, 0/12
	CEA	1/12
	EMA	1/12
	Chromogranin	1/1(rare positive cells)1, 0/12
	Synaptophysin	0/12
	CD20	0/11
	CD56	0/12
	CD99	0/12
	CD117	0/12
	CA19.9	1/12
	CA-125	1/1(focal)1, 1/12
	AFP	0/12
	bcl-2	0/12
	Calretinin	0/12
	CDX-2	0/12
	HCG	0/12
	Her2	0/12
	Napsin A	0/12
	MUC2	0/12
	MUC5AC	1/12
	MUC6	1/12
	M-GGMC-1	0/12
	p53	1/12
	p63	0/12
	PLAP	0/12
	S-100	0/12
	Sp-A	0/12
	TdT	0/12
	TTF-1	0/12
	Vimentin	0/12
	Ki-67	30%2

Differential diagnosis

metastatic adenocarcinoma including mucinous bronchoalveolar carcinoma
thymic germ cell tumour
thymic carcinoid with mucinous stroma: there is strong positivity for both chromogranin and synaptophysin. The mucin is of stromal type (hyaluronic acid).
mesothelioma
mucoepidermoid carcinoma

References

1 Choi, W. W., Y. H. Lui, et al. (2003). "Adenocarcinoma of the thymus: report of two cases, including a previously undescribed mucinous subtype." Am J Surg Pathol 27(1): 124-30.

2 Takahashi F, Tsuta K, Matsuno Y, et al. Adenocarcinoma of the thymus: mucinous subtype. Hum Pathol 2005; 36:219-23

This page last revised 1.1.2009.

©SMUHT/PW Bishop