Tumor-to-tumor metastasis of colorectal adenocarcinoma within a gonadotroph pituitary adenoma.
- 1Department of Endocrinology and Metabolism, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
- 2Department of Pathology, Moriyama Memorial Hospital, Tokyo 134-0081, Japan.
Abstract
Pituitary metastases are uncommon, and most cases originate from breast or lung cancer. Tumor-to-tumor metastasis, in which one neoplasm metastasizes into another, is particularly rare in the sellar region. We report a 66-year-old man with metastatic sigmoid colon adenocarcinoma treated with modified FOLFOX6 (5-fluorouracil, L-leucovorin, and oxaliplatin) plus panitumumab; extracranial disease was controlled, whereas a sellar mass initially suspected as a pituitary adenoma slowly enlarged over 2 years. Endocrine testing showed anterior hypopituitarism without arginine vasopressin deficiency. Endoscopic transsphenoidal surgery was performed for continued enlargement and diagnostic uncertainty. Histopathology demonstrated a gonadotroph pituitary adenoma infiltrated by colorectal adenocarcinoma, with extensive intermingling of the 2 components rather than discrete nests, favoring tumor-to-tumor metastasis over a collision tumor. The metastatic component consisted of viable tumor cells without necrosis or convincing treatment effect despite prolonged chemotherapy. This case underscores that metastatic tumor within a pituitary adenoma may enlarge despite favorable systemic therapy outcomes. Metastasis should therefore remain a key differential diagnosis for a sellar mass radiologically suggestive of a pituitary adenoma.
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BibTeX
@article{murasawa2026tumortotumor,
title = {{Tumor-to-tumor metastasis of colorectal adenocarcinoma within a gonadotroph pituitary adenoma.}},
author = {Shingo Murasawa and Fumiya Isozaki and Miku Fukasawa-Maeda and Shinobu Takayasu and Naoko Inoshita and Yukihiro Fujita},
journal = {JCEM case reports},
year = {2026},
month = oct,
doi = {10.1210/jcemcr/luag325},
url = {https://europepmc.org/article/MED/42923192},
note = {CC BY},
}
RIS
TY - JOUR
TI - Tumor-to-tumor metastasis of colorectal adenocarcinoma within a gonadotroph pituitary adenoma.
AU - Shingo Murasawa
AU - Fumiya Isozaki
AU - Miku Fukasawa-Maeda
AU - Shinobu Takayasu
AU - Naoko Inoshita
AU - Yukihiro Fujita
PY - 2026
DA - 2026/10/22
JO - JCEM case reports
DO - 10.1210/jcemcr/luag325
UR - https://europepmc.org/article/MED/42923192
AB - Pituitary metastases are uncommon, and most cases originate from breast or lung cancer. Tumor-to-tumor metastasis, in which one neoplasm metastasizes into another, is particularly rare in the sellar region. We report a 66-year-old man with metastatic sigmoid colon adenocarcinoma treated with modified FOLFOX6 (5-fluorouracil, L-leucovorin, and oxaliplatin) plus panitumumab; extracranial disease was controlled, whereas a sellar mass initially suspected as a pituitary adenoma slowly enlarged over 2 years. Endocrine testing showed anterior hypopituitarism without arginine vasopressin deficiency. Endoscopic transsphenoidal surgery was performed for continued enlargement and diagnostic uncertainty. Histopathology demonstrated a gonadotroph pituitary adenoma infiltrated by colorectal adenocarcinoma, with extensive intermingling of the 2 components rather than discrete nests, favoring tumor-to-tumor metastasis over a collision tumor. The metastatic component consisted of viable tumor cells without necrosis or convincing treatment effect despite prolonged chemotherapy. This case underscores that metastatic tumor within a pituitary adenoma may enlarge despite favorable systemic therapy outcomes. Metastasis should therefore remain a key differential diagnosis for a sellar mass radiologically suggestive of a pituitary adenoma.
SN - 2755-1520
ER -