Evaluation of suspected malignancies
Mikael Häggström [note 1]
For evaluation of suspected malignancies such as tumors, the most important aspect is whether it is benign or malignant. If malignant, then staging is necessary. There are generally specific criteria for various forms of tumors, which should be used whenever applicable, but following are some generalizations.
A general approach is to start looking at the slide which seems to contain most tumor (excluding any necrosis), facilitating a diagnosis, and shows what kind of cells to look for in the periphery.
Benign or malignant
|Microscopy||Almost no irregularities of cellular structures||Nuclear atypia:
For specific diagnoses by organ system, see anatomic diagram on Patholines Main page. This resource will give the main steps towards reaching a diagnosis, but before making a tumor diagnosis, always confirm with The WHO Classification of tumors, and generally an experienced pathologist as well until you feel confident.
Two relatively common forms of tumors are:
Gland-like tumors are mainly evaluated for cellular atypia, architectural dysplasia and invasion, and thereby classified into the following main categories:
- Hyperplastic lesions, lacking significant atypia
- Adenomas, which can range from mild to high-grade dysplastic, yet are not invasive
- Adenocarcinomas, with the main criterion being invasiveness. Evaluate specifically by location when possible. Some specific locations included in this resource:
For Spindle-cell tumors, the shape of the nuclei is a clue to the diagnosis, with the following tendency:
- Pointed on both ends: True fibroblastic tumors
- Pointed on one end and blunted on the other ("bullet-shaped"): Neural
- Blunted on both ends ("cigar-shaped"): Smooth muscle
- Triangular: Myofibroblastic
Evaluate specifically by location when possible, such as spindle-cell tumors of the midgut.
Further pinpointing of a specific tumor type is often attained by thinking of one or more possible diagnoses, and looking up their differential diagnoses, followed by comparing their microscopic descriptions and multiple micrographs with the case at hand. When two or more diagnoses seem to fit with the case at hand, consider performing immunohistochemistry. Find relevant target proteins that are expected to stain substantially differently between the possible diagnoses. If it's not evident from initial sources, you may use Immunoquery.com which will generally suggest the most relevant target proteins to distinguish the suspected conditions at hand.
Staging is generally done by TNM classification. Specific TNM systems should be used whenever applicable, mainly the manual by the American Joint Committee on Cancer (AJCC) if you can access it. Further information: Secrets . Otherwise, a general system may be used:
T: size or direct extent of the primary tumor
N: degree of spread to regional lymph nodes
M: presence of distant metastasis
Put your main focus on features that will determine the final stage. For example, if you see a lymph node involved by cancer, the presence or absence of lymphatic invasion is no longer critical, but rather the presence or absence of additional involved nodes or distant metastasis.
Determine if malignant cells are located close to, or even in, any surgical resection margins.
Lymphovascular invasion should always be mentioned. When present at margins, it does not count as tumor extension.
Typing and grading
Beyond determining overall malignancy diagnosis (such as adenocarcinoma), probable origin and staging, classification of tumors into a specific histopathologic type or grade is generally of relatively less value. In cases of clearly non-malignant tumors where it is difficult to determine the specific histopathologic type or grade, it is generally acceptable to conclude the evaluation and report it as such, unless the clinician specifically requests otherwise. For potentially malignant or high-risk tumors, typing and grading often still affects the management.
Additional slices are indicated in the following situations:
- Re-excision does not identify tumor cells in a clearly non-radical primary excision or biopsy.[notes 1]
- The most aggressive pattern is seen in the last available section, in which case more sections are indicated (from the same paraffin block if additional tissue is not available).
For cancers, generally include a synoptic report, such as per College of American Pathologists (CAP) protocols at cap.org/protocols-and-guidelines.
See also: General notes on reporting
- In such cases, step slices are taken rather than serial ones.