Controlling the Charge Density Wave Transition in Single-Layer TiTe2xSe2(1-x) Alloys by Band Gap Engineering.

Closing the band gap of a semiconductor into a semimetallic state gives a powerful potential route to tune the electronic energy gains that drive collective phases like charge density waves (CDWs) and excitonic insulator states. We explore this approach for the controversial CDW material monolayer (ML) TiSe2 by engineering its narrow band gap to the semimetallic limit of ML-TiTe2. Using molecular beam epitaxy, we demonstrate the growth of ML-TiTe2xSe2(1-x) alloys across the entire compositional range and unveil how the (2 × 2) CDW instability evolves through the normal state semiconductor-semimetal transition via in situ angle-resolved photoemission spectroscopy. Through model electronic structure calculations, we identify how this tunes the relative strength of excitonic and Peierls-like coupling, demonstrating band gap engineering as a powerful method for controlling the microscopic mechanisms underpinning the formation of collective states in two-dimensional materials.

Primary Adnexal Signet-Ring Cell/Histiocytoid Carcinoma.

An 84-year-old man presented with a 2-year history of a progressive left-sided ptosis. Examination demonstrated a mechanical ptosis and concentric constriction of the palpebral aperture. CT imaging revealed demonstrated diffuse soft tissue infiltration of the upper and lower eyelids with extension into the anterior orbit. This case was diagnostically challenging because of a history of multiple other primary tumors. However, clinicoradiologic and histopathologic findings were consistent with a diagnosis of primary adnexal signet-ring cell/histiocytoid carcinoma. The patient underwent surgical excision but local recurrence was noted 2 months postoperatively.

Keloidal atypical fibroxanthoma of the scalp.

Atypical fibroxanthoma (AFX) is a rare low-grade sarcoma that occurs mainly in the elderly and may recur locally. There are multiple variants including keloidal AFX (KAF). KAF is characterised by a proliferation of atypical spindled and epithelioid cells admixed with bizarre pleomorphic cells. These cells intersect among broad bands of keloidal collagen. AFX is a diagnosis of exclusion so a broad panel of immunohistochemical staining should be applied to rule out other differentials (squamous cell carcinoma (SCC), melanoma, leiomyosarcoma, etc). There is added difficulty with the diagnosis of KAF as it may mimic multiple keloidal lesions, including exuberant scarring, as in this case. p53 immunohistochemistry staining can be useful in highlighting the presence of tumour cells. Additionally, next generation sequencing can detect genetic mutations identified in clonal proliferations consistent with tumour formation. KAF is easily overlooked and it should be included in the differential diagnosis for keloidal lesions showing even mild atypia.

Should lymph nodes from colorectal cancer resection specimens be processed in their entirety?

AIMS: To quantify the benefit of processing each lymph node in its entirety in colorectal cancer specimens. METHODS: 391 consecutive cases were examined retrospectively to assess how often cases were upstaged to node positive disease by examining each node in its entirety. RESULTS: 7 out of 391 patients were upstaged by this method. However, of those patients, approximately three could have been detected by chance. Therefore, approximately 1% of cases were correctly upstaged. However, six of these seven patients also had at least one additional adverse prognostic factor, and would otherwise have been considered high risk Dukes' B cases. CONCLUSIONS: Processing all slices of each lymph node significantly increases laboratory workload and is of minimal clinical benefit.