Parathyroid carcinoma is an exceptionally uncommon endocrine neoplasm, accounting for less than 1% of parathyroid tumours and also a rare cause of primary hyperparathyroidism. Although this malignant lesion is usually slowly progressive, it is frequently associated with local recurrences and also with metastases involving the local lymph nodes or distant sites.
We present a 59-year-old male patient who developed a parathyroid carcinoma metastasis involving the anterior mediastinal lymph nodes and thymus remnants, 3 years after the primary tumour was identified and treated by surgical excision followed by chemo and radiotherapy. The patient presented with severe, symptomatic hyperparathyroidism and a gamma scan revealed increased uptake hyperfixation in the paratracheal lymph nodes. A lymphadenectomy was performed and the gross examination of the specimen showed a pinkish – white, firm, poorly circumscribed mass. The microscopic examination revealed an epithelial proliferation with a predominantly nodular/solid growth pattern, composed of cells exhibiting moderate nuclear pleomorphism, prominent nucleoli and high mitotic activity, involving two lymph nodes and thymus remnants. Upon immunohistochemical analysis, the proliferation showed positive staining for GATA 3, as well as a high Ki 67 index, whereas TTF 1 and thyroglobulin were negative in the tumour cells. Thus, the diagnosis of metastatic parathyroid carcinoma was established. The aim of this paper is to gain further knowledge about the histopathological and immunohistochemical features, as well as about the clinical behaviour of parathyroid malignant lesions, especially considering their rarity.

5-HT4 receptors are a G-protein-coupled family of re-ceptors coupled with Gs protein that stimulates the pro-duction of the intracellular signaling molecule cAMP. It has two isoforms (5-HT4S and 5-HT4L), differing in the length and sequence of their C-termini[1]. 5-HT4 are present both in the central nervous system and peripheral tissues
in the brain, are found mostly in basal ganglia and the hippocampus[2]. In the periphery, 5HT4 play an important role in the functioning of gastrointestinal tract, urinary bladder, heart and adrenal gland. Gastrointestinal 5-HT4 receptors potentiate peristalsis, and electrolyte secretion. In the urinary bladder, acti-vation of 5-HT4 receptors modulates cholinergic and purinergic transmission. Stimulation of atrial 5-HT4 receptors produces tachycardia and arrhythmias. In the adrenal gland, activation of 5-HT4 receptors releases cortisol, aldosterone and corticosterone[3]. [...]

Serotonin (5-hydroxytryptamine or 5-HT)is a mo-noamine neurotransmitter involved in regulating and modulating physiological and behavioral processes [1]. Serotonin also plays an important role in the functio-ning of enteric nervous system [2]. [...]

Pain is defined by IASP (International Association for the Study of Pain) as an unpleasant sensorial and emotional feeling which is produced by an actual or potential tissue injury. Chronic pain management is currently a major public health challenge throughout the world, especially for patients with oncologic disorders. Data show that up to 90 percent of cancer patients suffer from pain during the course of their illness and 50-80 percent receive an inadequate pain management. [...]